1. Field of the Invention
The present invention relates to a multiple-input multiple-output (MIMO) communication system, and in particular to MIMO transmit beamforming using singular value decomposition and pre-minimum mean square error.
2. Related Art
In a radio frequency communication system, the use of multiple antennas can increase data throughput without additional bandwidth or increased transmit power. In one antenna configuration called multiple-input multiple-output (MIMO), multiple antennas are used at both the transmitter and receiver. Specifically, a transmitter sends multiple streams by multiple antennas through a matrix channel to a receiver, which receives those multiple streams using its antennas. The matrix channel consists of all paths between transmit and receive antennas.
Beamforming, which changes the directionality of the antennas (transmit and/or receive antennas), can be used to achieve spatial selectivity and thereby improve the performance of a MIMO system. For transmit beamforming, one or more steering matrices can be applied to the data to be transmitted to ensure that signals transmitted from the transmit antennas arrive constructively at each specified receive antenna and destructively at receive antennas other than the specified receive antenna. These steering matrices can control the phase and amplitude of the signal transmitted by each antenna.